Centrifugal pump for contaminated liquids



Dec. 21, 1965 sc 3,224,376

CENTRIFUGALPUMP FOR CONTAMINATED LIQUIDS Filed Sept. 17, 1963 2 Sheets-Sheet 1 Fig. 1 Fig 2 l I M IN V EN TOR. 'HARA LD SCI-IADE 211 ZZZ? Dec. 21, 1965 H. SCHADE 3,224,376

GENTRIFUGAL PUMP FOR CONTAMINATED LIQUIDS Filed Sept. 17, 1963 2 Sheets-Sheet 2 Fig. 5- Fig.6

INVENTOR. HARA LD SCHADE United States Patent 3,224,376 CENTRIFUGAL PUMP FOR CONTAMINATED LIQUIDS Harald Schade, Frankenthalerstrasse 19, Karlsruhe, Baden, Germany Filed Sept. 17, 1963, Ser. No. 309,421 Claims priority, application Germany, Oct. 12, 1962, Sch 32,166 4 Claims. (Cl. 103-103) The present invention relates to a centrifugal pump for contaminated liquids.

It is already known generally to design centrifugal pumps for liquids which are contaminated by solids in a manner so as to disintegrate the solids to such an extent that neither the pump itself nor the subsequent pipe lines will be clogged. For this purpose, the impellers or propellers of these known pumps were provided with cutting elements which cooperated with fixed cutting elements on the pump housing. For compensating the wear of the cutting edges, the impellers or propellers and possibly also the fixed elements were adjustably mounted.

These known pumps have the disadvantage that the cutting elements are easily damaged by hard substances which are carried along in the liquid, for example, in the sewage, for example, by metal parts, stones, or the like, and that the pumps are thereby also frequently jammed. This leads to breakdowns in the operation, requires the replacement of the cutting elements, and may result in considerable damage and expense.

It is an object of the present invention to overcome these disadvantages by securing to the pump impeller at the side of the inlet opening of the pump a cutter ring which is rotatable with the impeller, is provided with openings corresponding to the inlet opening of the pump, and adapted to be exchanged when worn. This cutter ring cooperates with one or more movable cutter blades which are pressed by spring means against the cutter ring and are mounted so as to be able to yield toward the rear, that is away from the cutting surface of the cutter ring if the cutting resistance increases beyond a certain limit. The spring means acting upon the cutter blade are designed so that the movable cutter blade will yield only if very hard substances occur in the current of the liquid to be pumped whereas normally the cutter blade engages upon the cutter ring. The spring means are preferably provided in the form of a spring with a progressive spring characteristic which presses the cutter blade against the cutter ring only by means of a relatively small initial spring tension. This small initial tension permits softer substances to be cut up and the cutting edges to be reground continuously so that the unavoidable wear on these cutting edges will be compensated, while a stronger wear by friction will be avoided. If the current of liquid to be pumped carries along harder substances, the cutter blade yields, ie its distance from the cutter ring increases and as this distance increases the cutter blade will be acted upon by stronger spring forces which in cooperation with dynamic forces also permit very resistant substances to be cut up so as to pass into and through the pump without damaging or clogging the same. The particular resilient arrangement of the cutting elements relative to each other also prevents these elements from being damaged by harder substances and it also considerably reduces the cutting impacts and the stresses upon the bearings and couplings which are caused by such impacts.

The above-mentioned and numerous additional features and advantages of the present invention will become more clearly apparent from the following detailed description thereof, which is to be read with reference to the accom panying drawings, in which:

3,224,376 Patented Dec. 21, 1965 FIGURE 1 shows a general view of the pump and the disintegrating device;

FIGURE 2 shows a longitudinal section of the pump and the disintegrating device;

FIGURE 3 shows a cross section of the pump impeller and the disintegrating device on the line 33 of FIG- URE 1;

FIGURE 4 shows a bottom view of the pump;

FIGURES 5 to 8 show spring diagrams of the cutter blade; while FIGURES 9 to 12 show cross sections of diiferent modifications of the cutter ring.

As illustrated particularly in FIGURE 2 of the drawings, in the pump housing 1 a shaft 3 is rotatably mounted on which the pump impeller 2 is rotatably mounted and which is driven by the motor 5 through a resilient coupling 4. A cutter ring 6 is secured either to the impeller 2 as by Welding) or to the shaft 3 so as to be rotatable with the impeller. Cutter ring 6 is provided with apertures 7 which form the inlet openings of a size corresponding to the size of the inlet opening of the pump itself.

The outer edges of the apertures 7 which are facing in the forward direction of the rotation of the cutter ring 6 are inclined so as to form cutting edges. The lower end of the pump housing 1 is provided with eyes 9 in which a lever 10 on a shaft 11 is pivotably mounted. This lever 10 has a cutter blade 12 removably secured thereto so as to be easily exchangeable. Shaft 11 is spaced from the plane of the cutting surface and the cutter blade 12 can therefore pivot outwardly and away from the cutter ring 6 along an arc which is inclined to the cutter ring. The spring 14 presses the cutter blade 12 against the cutter ring 6 through the pressure on disc 13' secured to rod 13 which is pivoted at 10 to lever 10 shown in FIG. 4, the cutter ring turns in the direction of the arrow, so that the side edges 8 of the openings 7 cooperate with the side edge of the cutter blade 12 carried by lever 10.

As long as the pump only has to pump relatively clean water or other liquid, it operates as a normal centrifugal pump, and the water then passes through the cutter ring 6 and the impeller 2 into the diffuser 15 and then from the housing 1 through the outlet opening 16. If the flow of liquid contains solid substances which are larger than the apertures 7 of the cutter ring 6, they will be applied by the suction of the current of liquid against the outer surface of the cutter ring and be held thereon.

Due to the rotation of the cutter ring 6, these substances then pass to the cutter blade 12 and are cut up between the cutter ring 6 and blade 12 until they can pass through the apertures 7 in the cutter ring 6, into the pump housing. If these substances are so large or so solid that they can not be sumciently cut up by a single passage between the cutter ring 6 and the cutter blade 12, the cutter blade on lever 10 will pivotably yield against the action of spring 14 so that the cutting surfaces will not be damaged. By the rotation of the cutter ring 6 the solid substances will then be repeatedy passed into engagement with the cutter blade 12 until they are cut up sufliciently to pass through the apertures 7. If heavy substances such as metals, stones and the like are drawn upwardly into the cutting device by the suction of the current together with lighter adhering parts, such as textiles or the like, these heavy substances will sink against the ascending current into the sump of the pump underneath the pump housing, while the substances which are adhering to the cutter ring 6 are cut up. These heavy substances which are collected in the sump should occasionally be removed therefrom.

If, as illustrated in FIGURES 1 and 2, spring 14 is a normal coil spring with a straight characteristic, a spring diagram will result as shown in FIGURE 5, in which the ordinate 21 indicates the path of travel of the cutter blade 12 and the abscissa 22 indicates the force of spring 14. The point of intersection of the spring characteristic 23 with the abscissa 22 indicates the initial tension 24 with which the cutter blade 12 is pressed against the cutter ring. If instead of spring 14 a spring with a progressive characteristic is employed, the spring diagram will be as shown in FIGURE 6, in which the initial tension 24 with which the cutter blade 12 is pressed against the cutter ring 6 is so small that softer materials will be cut up and the cutting surfaces on the cutting ring and the cutter blade will continuously sharpen each other without excessive wear and therefore remain sharp for a long time, whereas when harder, more resistant substances occur, the cutter blade 12 will yield which will immediately result in an increase in the spring tension and a gradual cutting up of these substances. It is, of course, also possible to attain the progressive spring characteristic by replacing such a simple progressive spring by several springs with characteristics of a different pitch and a different initial tension.

FIGURE 7 shows the spring diagram of such a combination of a weak spring 25 with a strong spring 23 which is also provided with a strong initial tension. The cutter blade 12 then engages normally under the small initial tension 26 with the cutter ring 6, while when the cutter blade 12 yields for a distance 27, the strong spring 23 becomes effective.

In certain cases it may be advisable to reduce the initial tension of the cutter blade 12 against the cutter ring 6 This may be accomplished by providing a stop member, not shown, which is preferably adjustable during the operation of the pump and against which the lever is adapted to engage. The spring diagram resulting from the provision of such a stop member is shown in FIG- URE 8. The cutter blade 12 is then held at the adjustable distance 28, i.e. the cutting slot, from the cutter ring 6. Thus, there is no positive engagement between the cutter blade 12 and the cutter ring 6 and, therefore, no wear when no cutting action occurs. This means, however, that there is also no longer an automatic compensation of the increase in the size of the cutting slot which may be caused by wear, but this size has to be newly adjusted by hand after the cutter elements have become worn. Such an adjustment may, however, be carried out very easily.

In the event that due to the consistency of the contaminants a severe beating action of the cutter blade 12 might occur, the invention further provides parallel to the spring 14 a-preferably hydraulicshock absorber 14 acting on disc 13' which does not affect or only slightly affects the yielding stroke of the cutter blade 12, but dampens considerably the return stroke of the latter and, therefore, protects the cutting elements and the bearings from the knocks and impacts which would otherwise occur.

A modification of the invention consists in mounting the lever 10 so that its pivot axis 11 does not extend parallel to the cutting surface of cutter ring 6, as shown in FIGURE 2, but vertically or substantially vertically thereto. According to this embodiment of the invention, the pivot axis 11 therefore extends parallel or substantially parallel to the shaft 3 and the yielding movement of cutting blade 12 extends parallel or substantially parallel to the cutting surface of cutter ring 6. The manner of operation of the cutting mechanism is, however, basically the same as that which has been described with reference to FIGURES 1 and 2.

Although the pump according to the invention has so far been described as being provided with a fiat cutter ring 6, it may also be provided with an axially symmetrical cutter ring of any other suitable shape.

Thus, for example, FIGURE 9 illustrates a conical cutter ring and FIGURE 10 a cylindrical cutter ring, both of them being designed so that the current of liquid first passes through the insideof the ring in the direction as indicated by the arrows 31. The cutter blades 12 according to the invention may be easilyadapted to the cutter rings of these modified shapes. They have the advantage over a flat cutter ring according to FIGURES l to 4 that, even though they have the same outer diameter as the latter, they have a larger cutting surface and a larger liquid passage. However, especially in the embodiment according to FIGURE 10, the possibility of the cutter blade 12 to yield is limited since it has to move at the inside of the cylinder. This disadvantage is overcome if cutter rings according to FIGURES 11 and 12 are employed in which the current of liquid passes from the outside to the inside of the cutter ring, as also indicated by the arrows 31. Since in these cases the cutting operation occurs on the outside of the cutter ring, the cutter blade can move freely and the cutting surface and current passage is also very large. However, the pumping efficiency of a pump with cutter rings according to FIG- URES 11 and 12 is slightly lower than that of a pump with cutter rings according to FIGURES 1 to 4 and FIGURES 9 and 10 since the liquid must first be drawn toward the inside before it will be propelled outwardly by the impeller blades.

All of the embodiments of the cutter ring 6 as previously described have the important feature in common that the outer edges of the inlet apertures of the cutter ring 6 form the narrowest passage for the liquid current and that the cross-sectional area of flow thereafter increases continuously. Consequently, any solid substances which have passed through the inlet side of the cutter ring 6 can no longer cause any clogging in the channels of the impeller 4, in the diffuser 15, or in the outlet opening 16 of the pump housing.

In order to attain a more pleasing symmetrical appearance of the pump, the cross-sectional area of flow of the diffuser does not increase in the usual manner in the radial direction, but in the axial direction.

Another feature of the invention which is of importance for protecting the pump and especially the cutting elements from damage consists in the particular design and dimensions of the resilient coupling 4. It is the purpose of this coupling to insure that, in the event that the current of liquid to be conveyed by the pump contains substances such as pieces of metal, stones, and the like which cannot be cut up by the cutting elements and these substances pass between these cutting elements so that the cutting blade 12 is then pivoted outwardly and the impeller 2 is slowed down, the motor 5 and its shaft will continue to run at a substantially constant speed and will again accelerate the impeller 2 to its normal speed as soon as the part which cannot be cut up has been expelled from the cutting elements. For attaining this object, the following conditions should be fulfilled:

(1) The coupling 4 should at a maximum deflection of the lever 10 permit a static twisting of the coupling members by the distance of a considerable sector angle relative to each other.

(2) The inertia GD of the lever 10 and all masses connected thereto or reduced to its pivot axis should not be larger than the inertia GD of the pump impeller 2 and all parts which are rigidly connected thereto.

(3 The inertia GD of all revolving masses which are rigidly connected to each other above the resilient coupling 4, as seen in FIGURE 2, should not be larger than 0.25 GD The centrifugal pump according to the invention may, when built for a smaller output, also be employed as a waste and garbage disposal unit, for example, in connection with a trash rack. In such a case, it is advisable to divide the water current issuing from the pump by a suitable device into two branches, to pass one branch back into the channel and to pass the other branch into a trough behind the trash rack to flush the collected material in front of the inlet opening of the pump. A suitable separating device is then preferably employed, for ex ample, a hydrocyclone, which is adapted to pass the disintegrated material downwardly, while the liquid which is freed from the contaminants is used for flushing.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to the details of such embodiments, but is capable of numerous modifications within the scope of the ap pended claims.

Having thus fully disclosed my invention, what I claim 1. A centrifugal pump for conveying liquids contaminated with solids having a housing, an impeller rotatably mounted in said housing, means for driving said impeller, said housing having at least one inlet opening leading to said impeller, disintegrating means comprising a cutter ring removably secured to and rotatable with said impeller and disposed in front of said inlet opening, said cutter ring having apertures for the passage of liquids therethrough to said inlet opening, the outer edges of said apertures forming cutting edges, at least one cutter blade operatively associated with said cutter ring, spring means acting upon said cutter blade to press the same toward said cutter ring, means mounting said cutter blade so as to be movable relative to said cutter ring and to permit said cutter blade to yield against the action of said spring means when said disintegrating means are overloaded, and shock absorbing means for retarding the movement of said cutter blade toward said cutter ring after said cutter blade has yielded from said cutter ring.

2. A centrifugal pump for conveying liquids contaminated with solids having a housing, an impeller rotatably mounted in said housing, means for driving said impeller, said housing having at least one inlet opening leading to said impeller, disintegrating means comprising a cutter ring removably secured to and rotatable with said impeller and disposed in front of said inlet opening, said cutter ring having apertures for the passage of liquids therethrough to said inlet opening, the outer edges of said apertures forming cutting edges, at least one cutter blade operatively associated with said cutter ring, spring means acting upon said cutter blade to press the same toward said cutter ring, means mounting said cutter ring and to permit said cutter blade to yield against the action of said spring means when said disintegrating means are overloaded, said driving means comprising a motor having a shaft, a second shaft carrying said impeller, and a retary resilient coupling connecting said two shafts and adapted to permit said second shaft to turn resiliently about a considerably angle relative to said first shaft when said cutter blade has yielded to its maximum extent from said cutter ring.

3. A centrifugal pump as defined in claim 2, in which said mounting means comprise a lever pivotably mounted on said housing, said cutter blade being removably secured to said lever, the inertia GD, of said lever and all masses combined therewith as reduced to its axis not exceeding the inertia GD of said impeller and all parts rigidly connected thereto, and the inertia GD of all revolving masses intermediate said coupling and said motor and connected to said motor shaft as reduced to its axis not exceeding 0.25 GD 4. A centrifugal pump for conveying liquids contaminated with solids having a housing, an impeller rotatably mounted in said housing, means for driving said impeller, said housing having at least one inlet opening leading to said impeller, disintegrating means comprising a cutter ring removably secured to and rotatable with said impeller and disposed in front of said inlet opening, said cutter ring having apertures for the passage of liquids therethrough to said inlet opening, the outer edges of said apertures forming cutting edges, at least one cutter blade operatively associated with said cutter ring, spring means acting upon said cutter blade to press the same toward said cut-ter ring, means mounting said cutter blade so as to be movable relative to said cutter ring and to permit said cutter blade to yield against the action of said spring means when said disintegrating means are overloaded, said pump being employed as a trash disposal unit, and means for dividing the water issuing from said pump into two currents, one of said currents adapted to be used for flushing the trash toward said inlet opening of said pump and the other current being passed away from said pump.

References Cited by the Examiner UNITED STATES PATENTS 1,397,828 11/1921 Williams 241289 X 2,835,203 5/1958 Cliborn 103103 3,005,637 10/1961 Hetteen.

FOREIGN PATENTS 584,395 1/ 1947 Great Britain.

KARL I. ALBRECHT, Primary Examiner. HENRY F. RADUAZO, Examiner. 

1. A CENTRIFUGAL PUMP FOR CONVEYING LIQUIDS CONTAMINATED WITH SOLIDS HAVING A HOUSING, AN IMPELLER ROTATABLY MOUNTED IN SAID HOUSING, MEANS FOR DRIVING SAID IMPELLER, SAID HOUSING HAVING AT LEAST ONE INLET OPENING LEADING TO SAID IMPELLER, DISINTEGRATING MEANS COMPRISING A CUTTER RING REMOVABLY SECURED AND TO AND ROTATABLE WITH SAID IMPELLER AND DISPOSED IN FRONT OF SAID INLET OPENING, SAID CUTTER RING HAVING APERTURES FOR THE PASSAGE OF LIQUIDS THERETHROUGH TO SAID INLET OPENING, THE OUTER EDGES OF SAID APERTURES FORMING CUTTING EDGES, AT LEAST ONE CUTTER BLADE OPERATIVELY ASSOCIATED WITH SAID CUTTER RING, SPRING MEANS ACTING UPON SAID CUTTER BLADE TO PRESS THE SAME TOWARD SAID CUTTER RING, MEANS MOUNTING SAID CUTTE RBLADE SO AS TO BE MOVABLE RELATIVE TO SAID CUTTER RING AND TO PERMIT SAID CUTTER BLADE TO YIELD AGAINST THE ACTION OF SAID SPRING 